Page 1
Preface
This service manual covers the Tandberg tape recor-
der models l2-4 and 12-2.fhe model series l2 is a
fully transistorised, three speed stereo, record arrd
playback unit with two heads. lt is equipped with
separate record and playback preamplif iers and sepa-
rate power amplifiers for each channel. The power
output amplifiers are rated for l0 watts each.
The model 12 -2 is the two-track version while the
model I 2-4 is the four-track version. The models
12-2 and )2-4 have exaclly the same mechanical
system and operating controls.
We hope thot everyone concerned with our products
will find this service manual useful.
April 1967
1
1
Page 2
T'r
Contents
Technicol specificqlion, Tondberg tope recorder models
l2-4 ond l2-2 .
The function of the conlrols
The inpuf ond outpuf lerminols
The mechonism, detoiled descripiion ond odiusiment
instruciion
The operoling lever . .
4.I.1 The moior switch
1.1.2 lhe eccentric segment
4.1.3 The pressure wheel ossembly
4.1.4 The tope broke
4.1.5 The trip bor
4.2 The turnfoble ossemblies
^ 4.2.1 lhe supply turnfoble ossembly r 4.2.2 lhe lope iight lension .
4.2.3 The toke-up turntoble ossembly
A.2.4 Horizontsl ond veriicql olignments of the furntobles
1.3 Clulch olignments
4.3.1 Generol
4.3.2 Fost rewind
4.3.3 Fost wind
4.3.4 Normql forword drive . .
4.3.5 Neutrol
4.3.6 Free
4.4 fhe motor pulley
4.4.1 Threoding of the rubber drive belt
4.5 The speed lronsfer wheel
4.6 The lifting mechonism ..... . '.... '.. 19
5.2.1 The f unclion selecior swilch
5.2.2 lhe speoker selector swilch .
5.2.3 Monourol recording on CHI or CH2 , .
5.2.4 Mixing during monourol recording
5.2.5 Stereo recording
5.2.5 Monourol ploybock, chonnel I or 2 .. '....,.
5.2.7 Stereo ploybock 33
5.2.8 Stereo omplifier 33
5.2.9 Add o irock . 33
S.2,l0Sound on sound 34
5.3 Heod olignment ond frock conlrol with Tondberg test tope 34
5.3.I The Models l2-4 and 12-2 .......... 34
5.3.2 The model l2-2 35
1.0 3t
3l
32
32
33a?
33
32
35
a5
35
35
5.5
5.6
35
36
36
36
36
35
36
2.O
3.0
4.O
1.1
e
9
9't0
l0
12
t2
t2
IJ
l3
t4
l5
'15
't5
l6
l6
17
t7
l8
't8
l8
l8
JJ
JJAE )
4.9 The momenlqry stort-stop feoture
4.10 The pressure pqd . . .
4.l l The oulomotic end sfop switch .
4.12 The revolulion counler .
4.13 Assembling the fop cover
5.0 The electronic circuits, detoiled descriplion ond odiusfmenl
instruction
5.1.1 lnpuls
5,'I .2 The record pre-omplif ier
5.1.3 The FM multiplex-filter
5.1.4 The equolizing omplifier in record posiiion . '... ' 25
5.1.5 The equolizing omplifier in ploybock position . .. . 26
5.1.6 The equolizing omplifier in omplifier posilion . .. . 27
5.1,7 lhe power oulput omplifier 28
5.1.8 The ploybock pre-omplifier 29
5.1.9 The record level indicotor circuit .. 29
5,l.l0The oscillotor, bios ond erose circuit 29
5.l,ll The power supply 30
5.4 Heod olignment without Tqndberg test topes
5.4.1 Demognetizing
5.4.2 The odlustoble tope guides
5.4.3 The record/ploybock heod
5.4.4 The erose heod
Trock conlrol, model l2-4 without Tqndberg test lqPes . -
5.5,1 The record/ploybock heod
5.5.2 The erose heqd
Trock conlrol, model l2-2 without Tondberg lesi topes ..
5.6.1 The erose heod
5.6.2 The record/ploybock heod . .
Electrical qdiustments for Tondberg tope recorder models
12-4 ond 12-2 . .
5.7.1 Adiustment of ihe Power outPuf omplifier
5.7.2 Adiusfment of the outpui level
5.7.3 The quiescent currenl .
5.7.4 Adiustment of the FM MX-filter
5.7.5 Control of lhe frequency response in omp' position
5.7.6 The boss conlrol
5.7.7 The ireble control
5.7.8 ,Adiusfment of the record currenf ond the eleclronic
beqm indicotor circuits .
The electronic beqm indicolors
The record current.
Adivstment of the osc, frequency ond the bios ..
Dislortion
Bolonce odiustment of lhe pre-omP ouiPuts
Adiusiment of the equolizoiion coils Ll ond L2 '.
Control of the recording curves .
Control of the ploybock curves .
Control of the lotol frequency resPonse
Power oulpul control .
Speed test
36
36
5.7
1.7
1.9
The flywheel with ihe copston
4.7,1 The broke for the flywheel
The speed chonge mechonism . . .
20
21
) O 2l
22
22
22
22
24
24
25
25
36
1A
37
382a
Jd
39
39
39
5.7.9
5.7. r 0
5.7 .t I
5.7.12
5.7.13
5.7.1 4
5.7.15
5.7.16
5.7.17
5.7.18
5.7.19
'l
,1
i .t
ttT t{tI
tt
5.8 Electricol modificotions introduced to the tope recorder
model 12 ... .. . .. ' 40
5,9 Modificolions from four-trock to iwo-frock models . . . . . . 41
5.10 Modificofions from 220 volts 50 c/s to ll0 volfs 60 c/s .. 4l
6.0 Ports list .'.....". 4l
6.0.1 Mechonicol ports 4l
6.0.2 Elecrricol ports ' . 46
